You need to do PASV FTP transfers to get through the firewall... I think one of the dash's supports PASV, UnleashX supports PASV, others may as well.
Otherwise you're kinda boned.
Hey Reval, I cant actually help you with your question (sorry!) but what you've posted interests me. I'm a devoted Mac user at work (Panther 10.3.8) but I figured I was going to have buy a Windows PC for use at home as I want to set up FTP with my modded X-box. By the sounds of it though, you've got an xbox-to-Mac connection up and running. Any chance you could give me a brief outline of how to do this? Thanks, JonBOY.
FTP is FTP, it doesn't really matter what platform you're running on. I use my Mac to connect to my XBOX all the time. I reccomend Transmit (#1), CuteFTP (#2), or FTPeel(#3).
There are also some very decent XBOX utilities that run in OS X (check macupdate).